2. Histopathology and radiology

Question 1

What are the 2 broad categorisations of mature bone?

Answer 1

Cortical

Cancellous

Question 2

What % of bone is cortical and where is cortical bone most abundant?

Answer 2

80% of bone

Long bones

Question 3

Describe the structure of cortical bone

Answer 3

Mature, lamellar bone - PARALLEL lamellae

Question 4

Describe the structure of cancellous bone

Answer 4

Mature, lamellar bone - CONCENTRIC lamellae

Question 5

What is the primary function of cancellous bone and where is it most abundant?

Answer 5

Metabolic fx - can dissolve/ resorb quickly for Ca++ homeostasis
Vertebrae and pelvis

Question 6

Describe the process of mineralisation

Answer 6

Process through which an organic substance becomes impregnated by inorganic substances

Question 7

What name is given to immature bone? Describe it structure

Answer 7

Woven bone

Irregularly-arranged collagen

Question 8

What are the cannaliculae in bone?

Answer 8

Communication channels for osteocytes

Question 9

What can be seen where there is osteoclast activity?

Answer 9

Howship’s lacunae

= “bite-marks” where breakdown is occuring

Question 10

Recall the relative proportions of organic and inorganic matter in bone, and summarise the composition of each of these

Answer 10

Organic (cells and protein matrix) = 35%

Inorganic (Ca hydroxyapatite) = 65%

Question 11

What is the role of the RANK ligand in bone homeostasis?

Answer 11

When RANK combines with RANK-L osteoclasts are stimulated to differentiate

Question 12

By what mechanism is osteoclast action inhibited?

Answer 12

Osteoprotegerin

Inhibitor of RANK:RANK-L binding

Question 13

Where are osteocytes located in bone?

Answer 13

Lacunae

Question 14

Distinguish between primary and secondary osteoperosis

Answer 14

Primary = age-related, post-menopause
Secondary = caused by drugs (eg thyroid drugs) or systemic disease

Question 15

Recall the key distinguishing features of osteoperosis from other metabolic bone diseases

Answer 15

NORMAL mineralisation so serum biochemistry is normal - just a reduced mass of bone

Question 16

What is raised ALP indicative of? Give 4 examples of where this might be seen

Answer 16

Increased bone turnover

1. Paget’s
2. Osteomalacia
3. Bony Mets
4. HyperPTHism

Question 17

Sumamrise the possible radiological findings in osteoperosis

Answer 17

MAY BE NORMAL
OR
1. Osteopaenic
2. Osteosclerotic

Question 18

Why might osteoperosis demonstrate osteopaenia

Answer 18

Loss of bone quantity rather than quality

Question 19

How does osteopaenia appear radiologically?

Answer 19

Reduced opacity

Question 20

What is osteosclerosis?

Answer 20

Increased bone density

Question 21

Recall 2 key features of osteomalacia radiologically

Answer 21

1. Looser’s zone fractures (horizontal fracture in cortical bone)
2. Codfish vertebrae
   (biconcave vertebrae)

Question 22

Recall 2 radiological features of Paget’s disease

Answer 22

1. Cortical thickening

2. Coarsening trabeculae

Question 23

Describe how primary and secondary hyperPTHism can be distinguished radiologically?

Answer 23

Primary = bone resorption
Secondary = bone resorption AND INCREASED DENSITY
Bone resorption has appearance of erosion, and can lead to “brown tumour”

Question 24

What is renal osteodystrophy?

Answer 24

Comprises all the skeletal changes of CKS - a combo of:
OsteoMALACIA
OsteoSCLEROSIS
OsteoPEROSIS
OsteoTITIS FIBROSIS CYSTICA

Question 25

Describe the serum biochemistry of renal osteodystrophy (phosphate, calcium, PTH, pH)

Answer 25

HIGH phosphate LOW calcium HIGH PTH Metabolic acidosis

Question 26

How does sclerosis appear radiologically?

Answer 26

Rugged vertebrae (Jersey spine)

Question 27

Recall 3 radiological features of renal osteodystrophy

Answer 27

Brown tumour Jersey Spine Soft tissue calcification around vessels

Question 28

Recall 2 radiological features of Rickets

Answer 28

Cupped and frayed metaphysis due to increased stress | Widenened unmineralised growth plate